Physicochemical and combustion characteristics of pyrolyzed coal and biocoal briquettes via thermogravimetric analysis

Pyrolysis is highly regarded as a means to produce smokeless briquettes. This study investigated the effects of torrefaction and fast pyrolysis on the physicochemical and combustion characteristics of coal and biocoal briquettes. Biocoal briquettes were prepared with coal dust and rice husks using cassava starch gel as a binder, whereas no biomass was used for coal briquettes. The feedstocks were compacted in a briquetting machine and then dried in a solar dryer before pyrolysis in a muffle furnace fitted with a vacuum system. The proximate compositions were derived from thermogravimetric analysis (TGA), and the calorific values were calculated. The combustion characteristics were determined through thermogravimetry (TG-DTG) analysis. The functional groups were analyzed via Fourier transform infrared (FTIR) spectroscopy. The results revealed that biocoal briquettes with coal-to-rice husk ratios of 50:50 and 60:40, which were subjected to torrefaction for 30 min at 200°C, had the same volatile matter content (12%), but differed in other properties. The pyrolyzed coal briquette exhibited the highest flammability and combustion indices. Furthermore, some transmittance peaks shifted to lower or higher frequencies. This study demonstrates that the the properties of pyrolyzed briquettes are influenced by the pyrolysis temperature, feedstock and blending ratio.